1. Field of the Invention
The present invention relates to a communication navigation system and a communication navigation method for vehicle use or the like, which can perform navigation processing, such as route search, route navigation, map display, and the like, at least partially by using a communication network, as well as a program storage device and a computer data signal embodiment in a carrier wave.
2. Description of the Related Art
Nowadays, research and development on electronic control for controlling the drive of a vehicle are advanced, and navigation systems for aiding in driving are significantly spread and popularized. This navigation system generally has various databases and such a basic structure that displays, on a display device, map information, current position information, various guidance information, and the like. Moreover, it searches for a drive route on the basis of an inputted condition.
A function called as a xe2x80x9croute searchxe2x80x9d or xe2x80x9cpath searchxe2x80x9d of a navigation apparatus mounted on a vehicle is designed to be capable of searching for an optimum route connecting an origin and a destination, both of which are designated by a user. It is also designed to lead and guide (navigate) the user to the destination by displaying on a map a current position based on a self-contained or built-in positioning measurement or a GPS (Global Positioning System) measurement and the searched optimum route.
With respect to a traditional navigation apparatus, this kind of route search is performed by microprocessor processing in the apparatus on the basis of the map database information stored in a map information record medium (e.g. a DVD-ROM) equipped in the navigation apparatus. More concretely, the route search is executed by using xe2x80x9cinformation for a route searchxe2x80x9d, which enables a search for the optimum route based on predetermined mathematical algorithm, such as link information corresponding to a road part between branching points and intersections, node information including coordinates information (e.g., absolute position information on latitude and longitude, or on altitude, latitude and longitude) corresponding to the branching points and the intersections of roads or the like among the map database information. Generally, in view of its nature of being for route search, this kind of information for a route search is constructed by the link information, the node information, and the like, which are about broad areas where roads are mutually connected, for example, such as throughout Honshu or the main island of Japan, throughout Japan, or the like, so that its volume of data becomes enormous, which increases the whole amount of data of the map database information.
Moreover, the map database information includes data of added information, which may be facility guidance information on tourist attractions/facilities, facility numerals, names (characters) of maps/roads, views of waters/railroads, and roads, in each one of many pieces of map information (drawings). These data as well as the above-described information for the route search further increase the volume of data of the map database information.
By the way, the search for the optimum route requires the newest map database information because of changes, new constructions, and the like on roads.
Therefore, there is a need to equip for the traditional navigation apparatus a map information record medium that stores the map database information which is the newest and whose data volume is enormous. At the same time, there is a need of the display processing and the search processing of the optimum route based on the complicated map database information. In this case, there is a need to mount a microprocessor unit (MPU), which is capable of high-speed processing, so that the scale of the processing and that of the apparatus come to increase.
On that account, various communication navigation systems are suggested in order to improve such increase of the scale of the processing and that of the apparatus. In these communication navigation systems, the map database information is obtained and provided through two-way wireless communication between a communication center apparatus on a communication network and a communication navigation terminal mounted on a vehicle (e.g. refer to the examples of Japanese Patent Application Laying Open NO. Hei 7-262493 xe2x80x9ca system for distributing map information for a movable bodyxe2x80x9d and Japanese Patent Application Laying Open NO. Hei 10-96644 xe2x80x9ca system for guiding a moving routexe2x80x9d).
The communication center apparatus in the communication navigation system in this kind can quickly and cheaply provide the newest map database information, because, for example, all we need is update the map database information of one communication center apparatus to the newest information, comparing to the case of providing an information record medium, which stores the newest map database information, for an individual navigation apparatus mounted on a movable body. Therefore, users side becomes able to receive the map database information including the newest information for the route search or the like.
Moreover, there has been developed such a communication navigation system that is designed not to perform the route search on the side of the communication navigation terminal, but to transmit information indicating a current position or an origin and a destination on the side of the communication navigation terminal, to perform the route search according to these by a high performance processor on the side of the communication center apparatus, to receive this search result and display it in a predetermined format on the side of the communication navigation terminal and so on.
However, the above-described communication navigation system has the following disadvantage.
It is impossible to have a service of navigation in the area that an electric wave cannot arrive in with a sufficient electric field intensity to use a wireless device. Usually, in this situation, there is no problem while driving along a route of a preset drive plan, however, in the case of deviating from the route by some reasons, if the area is out of a service area, it becomes impossible to obtain information to return the original route. For example, if it is impossible to transmit and receive the necessary information for the route search, then it is impossible to perform a route search to return to the route from which the movable body has deviated (hereinafter, such a route search is referred to as a xe2x80x9creroute searchxe2x80x9d as the occasion demands) on the side of the communication navigation terminal. Alternatively, if it is impossible to receive information on a current position or the like, then it is impossible to perform the reroute search on the side of the communication center apparatus. Moreover, if it is impossible to transmit and receive the search result, there is no meaning to perform the reroute search. Particularly, a movable body communication network is placed along expressways and main highways in many cases, and once the movable body deviates from this road, it is impossible to communicate, which is sufficiently assumed. Moreover, in the current situation, the infrastructure of a communication device such as a cellular phone or the like is not sufficiently promoted in mountain areas, and even in the future, it is difficult to think of the possibility to promote the infrastructure to cover all districts including depopulated areas, in the view of economic investment efficiency.
On that account, it is extremely important to construct a device for executing some navigation processing, such as searching for a route or a direction to be traveled, providing the search result, and the like, even if a vehicle enters into the area that it cannot communicate from its communication terminal, when expanding the use of the communication navigation system.
It is therefore an object of the present invention to provide a communication navigation system and a communication navigation method, which enable a search for a route to be traveled or the like, even if a movable body such as a vehicle or the like goes out of a service area of the communication navigation system, as well as a program storage device and a computer data signal embodiment in a carrier wave.
The above object of the present invention can be achieved by a first communication navigation system provided with: a communication center apparatus; and a communication navigation terminal, both of which transmit and receive information by a two-way communication through a communication network, (i) the communication center apparatus provided with: a map database for storing therein map database information including information for a route search, which enables the route search from a current position of a movable body to a destination by a predetermined algorithm; a search device for searching, by the predetermined algorithm, for a route heading to the destination from the current position, on the basis of the map database information including the information for the route search, according to the destination and the current position received through the communication network; and a center side wireless device for wirelessly transmitting route information indicating the searched route through the communication network, (ii) said communication navigation terminal provided with: a measurement device for measuring the current position; a terminal side wireless device for transmitting the measured current position and receiving the transmitted route information through the communication network; a traveling locus recording device for recording a traveling locus of the movable body such that it preferentially holds the traveling locus recorded when the movable body is moving out of a service area of the communication navigation system; and a processing device for performing navigation processing of a predetermined type based on the preferentially held traveling locus in case that the movable body is moving out of the service area.
According to the first communication navigation system of the present invention, the communication center apparatus is provided with the map database. This map database stores large-scale map database information including the information for the route search such as the above-described node information, link information, or the like, which enables a search for an optimum route from an origin to a destination by predetermined mathematical algorithm such as Dijkstra""s algorithm and so on. When the communication navigation is performed, route search request information indicating an origin and a destination may be firstly transmitted by a user communication terminal such as a cellular phone, a mobile, a facsimile, a personal computer, or the like at a user""s home, a communication navigation terminal, which is carried by a user or which is mounted on a user""s movable body, and so on. Secondly, the communication center apparatus receives this information through the communication network. Then, at the communication center apparatus, the search device searches for the optimum route with respect to the received route search request information with the predetermined algorithm such as Dijkstra""s algorithm or the like on the basis of the information for the route search included in the above-described map database information. Then, the center side wireless device wirelessly transmits, through the communication network, the searched information, including information on a plurality of guidance positions, for example, such as a branching point, an intersection, or the like, located on this searched route. In this specification, the xe2x80x9cguidance positionxe2x80x9d is referred to a position at which it is preferable to perform the route navigation or the route guidance of some kind in order to drive on a predetermined route. Moreover, the xe2x80x9cinformation on guidance positionsxe2x80x9d is information that allows the specification of locations of the guidance positions somehow, such as coordinates information that indicates absolute locations of the guidance positions, coordinates information that indicates relative locations with the absolute location as a standard, and the like.
On the side of the communication navigation terminal, the terminal side wireless device receives the route information indicating the optimum route from the current position to the destination, which has been transmitted from the center side wireless device of the communication center apparatus. This route information is recorded in the communication navigation terminal, and it is read out and displayed when the processing device performs the navigation processing such as route display, map display including the route, route navigation, route guidance, and the like. Map information for display used in this case can be obtained such that when the optimum route is presented from the communication center apparatus, the related map information within a predetermined range is transmitted at the same time. In this case, the map information for display can decrease in the volume of data to be transmitted and received, by cutting the related information within a predetermined range from the map database information including the information for the route search, whose data volume is huge, and transmitting it, and thus a recording device of the communication navigation terminal may be small. Alternatively, if the simple map information having small data volume is available, the map information may be stored in a storing device such as a DVD or the like equipped for the communication navigation terminal, and a related part may be read out from this.
Moreover, the communication navigation terminal is provided with a measurement device for measuring the current position. This is constructed by, for example, a GPS measurement device or a self-contained or built-in positioning apparatus for detecting a velocity, an acceleration velocity, an angular velocity, and the like, which is mounted on the movable body.
Here, the traveling locus recording device, which is constructed by, for example, a RAM, a hard disk, a DVD-RAM, and the like and which is equipped for the communication navigation terminal, records the traveling locus of the movable body. This recording may be or may be not performed within the service area of the communication navigation system, but at least, it is performed out of the communication navigation system. Then, especially with respect to the traveling locus recorded when the movable body is moving out of the service area, it is preferentially held. Then, in case that the movable body is moving out of the service area, the processing device performs the navigation processing of the predetermined type based on the preferentially held traveling locus, held by this traveling locus recording device. Namely, out of the service area, it is difficult or impossible to execute the route search on the communication center apparatus through the communication network. Besides, in view of the nature of the communication navigation, there are basically fewer information sources to search for a route and a direction to be traveled on the side of the communication navigation terminal. That is why the traveling locus, which is held by the traveling locus recording device in the past, is extremely helpful this time as the information source to search for the route and the direction to be traveled, out of the service area where the communication network cannot be used.
Incidentally, although the traveling locus is more or less recorded in traditional on-vehicle navigation systems, this is recorded without questioning whether it is within or out of the service area and the old ones are sequentially deleted while storing the new ones. Moreover, it is impossible for those traditional systems to hold the traveling locus out of the service area where the communication network cannot be used as the useful information source.
On the contrast, according to the present invention, since the traveling locus out of the service area is preferentially held by the traveling locus recording device, even in case that the movable body drives out of the service area later, it becomes possible to perform the navigation processing of the predetermined type, such as the search for the route and the direction to be traveled and the like, on the basis of this preferentially held traveling locus. For example, even out of the service area, it is possible to execute the processing relatively easily on the basis of the traveling locus in the past, such as the route search to a specified destination which has been visited in the past, the route search for a return route, and the like.
As described above, the first communication navigation system of the present invention, in which the communication navigation terminal mounted on the movable body is simply constructed with essential functions, is intended to execute the navigation processing, such as the route search and the like, by using the traveling locus in the past, even if the movable body goes out of the service area of the communication navigation system, in which the searching and operating functions in high quality requiring time are installed at the communication center apparatus.
In one aspect of the first communication navigation system of the present invention, the traveling locus recording device records the traveling locus with information indicating within or out of the service area.
According to this aspect, it becomes possible to treat with the traveling loci within and out of the service area of the communication navigation system while dividing or identifying them easily. Namely, the traveling locus out of the service area is helpful for the route search or the like when the movable body is out of the service area. On the other hand, if the movable body is within the service area, apparently, the communication center apparatus is accessed to perform the route search or the like, so the availability of the traveling locus is low.
In another aspect of the first communication navigation system of the present invention, the traveling locus recording device deletes the traveling locus recorded when the movable body is traveling within the service area, in an order from old to new one.
According to this aspect, in case that the route search or the is like is executed at the communication navigation terminal, it becomes possible to hold the locus data of the outer service area more, by the amount of deleting the traveling locus within the service area, which gives major effect to the route search out of the service area or the like. Moreover, even about the traveling locus within the service area, it is possible to hold, to some degree, the one which is relatively highly useful since it is new.
In another aspect of the first communication navigation system of the present invention, the traveling locus recording device gives priority to recording the traveling locus out of the service area than to recording the traveling locus within the service area until the traveling locus out of the service area occupies a predetermined ratio of a record area of said traveling locus recording device, and the traveling locus recording device replaces the traveling locus in an order from old to new one.
According to this aspect, it becomes possible to record the traveling locus within the service area at a predetermined ratio at the traveling locus recording device. Moreover, it prevents all of the recorded traveling loci from becoming the ones out of the service area.
In another aspect of the first communication navigation system of the present invention, the traveling locus recording device is equipped with a first record area for recording the traveling locus within the service area and a second record area for recording the traveling locus out of the service area and replaces the traveling locus in an order from old to new one respectively in the first and second record areas.
According to this aspect, the traveling locus within the service area can be recorded and held in the range of the first record area capacity, and the traveling locus out of the service area can be recorded and held in the range of the second record area capacity. Thus, it is prevented that all of the recorded traveling loci become the ones out of the service area, and at the same time, and the search of the data of the outer service is quickly performed. As for the first and second record area capacities, the whole record capacity may be distributed at a predetermined rate, considering their importance. Moreover, as for rewriting, the new traveling loci are replaced in the order to old to new one in each area.
In another aspect of the first communication navigation system of the present invention, the navigation processing of a predetermined type is processing of searching for at least one of a route and a direction to be traveled by the movable body, from the measured current position and the preferentially held traveling locus.
According to this aspect, out of the service area, it is possible to search for the route and the direction to be traveled by the movable body, on the basis of the traveling locus in the past, which is preferentially held by the traveling locus recording device.
The above object of the present invention can be achieved by a second communication navigation system provided with: a communication center apparatus; and a communication navigation terminal, both of which transmit and receive information by a two-way communication through a communication network, (i) the communication center apparatus provided with: a map database for storing therein map database information including information for a route search, which enables the route search from a current position of a movable body to a destination by a predetermined algorithm; a search device for searching, by the predetermined algorithm, for a route heading to the destination from the current position, on the basis of the map database information including the information for the route search, from the destination and the current position received through the communication network; and a center side wireless device for wirelessly transmitting route information indicating the searched route through the communication network, (ii) the communication navigation terminal provided with: a measurement device for measuring the current position; a terminal side wireless device for transmitting the measured current position and receiving the transmitted route information through the communication network; a traveling locus recording device for recording a traveling locus of the movable body; and a processing device for searching for at least one of a route and a direction to be traveled by the movable body as navigation processing of a predetermined type based on the measured current position and the recorded traveling locus in case that the movable body is moving out of the service area.
According to the second communication navigation system, which is different from the case of the above described first communication navigation system of the present invention, the traveling locus recording device records the traveling locus of the movable body without questioning whether it is within or out of the service area. Then, out of the service area, the processing device searches for at least one of the route and the direction to be traveled by the movable body, on the basis of this recorded traveling locus and the current position measured by the measurement device. Namely, comparing to the above described first communication navigation system of the present invention, in case that the movable body travels one area, which is out of the service area, the possibility of the traveling locus, which was obtained when having traveled within the same area in the past, being recorded in the traveling locus recording area becomes low. However, if there is the traveling locus, it becomes still possible to surely search for at least one of the route and the direction to be traveled on the basis of this recorded traveling locus and the current position.
Incidentally, although the traveling locus is more or less recorded in traditional on-vehicle navigation systems, it is impossible for those traditional systems to use the traveling locus out of the service area where the communication network cannot be used, as the useful information source to search for the route and the direction to be traveled, out of the service area.
As described above, the second communication navigation system of the present invention, in which the communication navigation terminal mounted on the movable body is simply constructed with essential functions, is intended to execute the navigation processing, such as the route search and the like, by using the traveling locus in the past, even if the movable body goes out of the service area of the communication navigation system, in which the searching and operating functions in high quality requiring time are installed at the communication center apparatus.
In another aspect of the first or second communication navigation system of the present invention, the communication navigation terminal is further provided with a judgment device for judging whether the current position is within or out of the service area.
According to this aspect, in case that the movable body goes out of the service area of the communication navigation system, in response to that, it becomes possible to appropriately deal with the route navigation, the simple navigation, the route search, and the like by automatic or manual operations.
In one aspect provided with the above described judgment device, it may be constructed such that the judgment device judges on the basis of an electric field intensity of an electric wave received by the terminal side wireless device.
By constituting in this manner, if the electric field intensity level of the electric wave received by the terminal side wireless device of the communication navigation terminal is low and information cannot be transmitted in sufficient quality, it is judged out of the service area of the communication navigation. If judged out of the service area, it is possible to automatically perform the navigation processing based on the traveling locus recorded in the traveling locus recording device, or it is possible to inform the fact of a driver by displaying it on the display device of the communication navigation terminal, alarming with a speaker, or the like.
In another aspect provided with the above described judgment device, it may be constructed such that the judgment device judges by transmitting a predetermined data row to the communication center apparatus from said communication navigation terminal, restoring the received data row at the communication center apparatus and transmitting it back to the communication navigation terminal, and then comparing the received data row with the transmitted data row at the communication navigation terminal.
By constituting in this manner, the communication navigation terminal judges whether the current position is within or out of the service area by emitting a signal for checking to the communication center apparatus, receiving and analyzing a signal for replying which has been transmitted, and judging whether or not the communication quality is sufficient. For example, it transmits predetermined data and has the communication center apparatus transmitted the data back. After receiving the data, it compares the transmitted data with the received data to obtain the frequency of errors and judges whether the current position is within or out of the service area. In this manner, it is possible to judge whether or not it is possible to have a service in the total communication system including the condition of the communication center apparatus in addition to the condition of the wireless communication network, which becomes a communication medium.
In another aspect provided with the above described judgment device, it may be constructed such that a judgment of the judgment device is performed at a predetermined time interval.
By constituting in this manner, the terminal side wireless device of the communication navigation terminal receives a carrier wave of a wireless line at predetermined time intervals and monitors its electric field intensity while the movable body is driving. If the electric field intensity level is equal to or lower than a predetermined level, it is judged out of the service area.
In another aspect provided with the above described judgment device, it may be constructed such that a judgment of the judgment device is performed at a predetermined driving distance interval.
By constituting in this manner, the terminal side wireless device of the communication navigation terminal receives a carrier wave of a wireless line and monitors its electric field intensity every time the movable body drives a predetermined distance while the movable body is moving. If the electric field intensity level is equal to or lower than a predetermined level, it is judged out of the service area. According to this method, it becomes possible to omit the operation of judgment regardless of the case of rarely driving because of traffic congestion. Moreover, it becomes possible to sufficiently understand the first driving distance after the movable body goes out of the service area.
In another aspect provided with the above described judgment device, it may be constructed such that the processing device performs the navigation processing of the predetermined type in case that the current position is judged to belong out of the service area by the judgment device.
By constituting in this manner, in case that the current position is judged to belong out of the service area by the judgment device, the processing device automatically performs the search for the route and the direction to be traveled and the like, on the basis of the traveling locus in the past, which is recorded in the traveling locus recording device Therefore, in the eyes of users, it is possible to obtain a screen display and/or an audio output of the route guidance or the like as a result of the navigation processing, without being aware of whether or not the current position is out of the service area.
In another aspect of the first or second communication navigation system of the present invention, the system is further provided with a user communication terminal for performing a two-way communication on the communication network, the user communication terminal being capable of transmitting the destination to said communication center apparatus.
According to this aspect, the user communication terminal, such as a personal computer, a facsimile, a mobile, a cellar phone, and the like, which are installed at the user""s home, transmits the route search request information, and the center side wireless device receives this route search request information. Since the route that meets the condition presented by the user is searched for on the basis of this information at the communication center apparatus, it becomes possible to request the route search before the user actually starts moving. The searched route information may be transmitted or transported to the communication navigation terminal through the wireless communication device directly from the communication center apparatus. It may also be transported to the communication navigation terminal after stored in the user communication terminal once. The transportation to the communication navigation terminal from the user communication terminal may be performed with a wireless device or through a memory medium such as a magnetic record medium, a semiconductor memory, or the like.
The above object of the present invention can be achieved by a communication navigation terminal included in the above described first or second communication navigation system (including its various aspects).
According to the communication navigation terminal of the present invention, it is possible to establish the above described first or second communication navigation system of the present invention by the use of this with the communication center apparatus and the communication network related to the present invention as described above. Moreover, even if a lot of communication navigation terminals are connected to the same communication center apparatus, each of them can obtain the benefit from the communication navigation system.
The above object of the present invention can be achieved by a first program storage device readable by a computer for tangibly embodying a program of instructions executable by the computer, which causes the computer to function as the communication navigation terminal in the above-described first or second communication navigation system (including its various aspects), more concretely, at various constitutional elements, such as the measurement device, the terminal side wireless device, the traveling locus recording device, the processing device and the like, which constitute the communication navigation terminal.
According to the first program storage device, the above described communication navigation terminal of the present invention can be relatively easily realized as a computer reads and executes the program of instructions from the program storage device such as a CD-ROM (Compact Disc-Read Only Memory), a DVD-ROM (DVD Read Only Memory), a hard disc or the like, or as it executes the program of instructions after downloading the program through communication device.
The above object of the present invention can be also achieved by a first computer data signal embodied in a carrier wave and representing a series of instructions which causes a computer to function as the communication navigation terminal in the above-described first or second communication navigation system (including its various aspects), more concretely, at various constitutional elements, such as the measurement device, the terminal side wireless device, the traveling locus recording device, the processing device and the like, which constitute the communication navigation terminal.
According to the first computer data signal embodied in the carrier wave of the present invention, as the computer downloads the program in the computer data signal through a computer network or the like, and executes this program, it is possible to realize the above described communication navigation terminal of the present invention.
The above object of the present invention can be achieved by a second program storage device readable by a computer for tangibly embodying a program of instructions executable by the computer, which causes the computer to function as the above described first or second communication navigation system (including its various aspects), more concretely, on one hand, at various constitutional elements, such as the map database, the search device, the center side wireless device and the like, which constitute the communication center apparatus, and on the other hand, at various constitutional elements, such as the measurement device, the terminal side wireless device, the traveling locus recording device, the processing device and the like, which constitute the communication navigation terminal.
According to the second program storage device, the above described first or second communication navigation system of the present invention can be relatively easily realized as a computer reads and executes the program of instructions from the program storage device such as a CD-ROM, a DVD-ROM, a hard disc or the like, or as it executes the program of instructions after downloading the program through communication device. For example, the communication navigation terminal may be constructed such that it has a browser function and that the computer program to use is substantially or partially provided from the side of the communication center apparatus, as occasion demands.
The above object of the present invention can be achieved by a second computer data signal embodied in a carrier wave and representing a series of instructions which causes a computer to function as the above described first or second communication navigation system (including its various aspects), more concretely, on one hand, at various constitutional elements, such as the map database, the search device, the center side wireless device and the like, which constitute the communication center apparatus, and on the other hand, at various constitutional elements, such as the measurement device, the terminal side wireless device, the traveling locus recording device, the processing device and the like, which constitute the communication navigation terminal.
According to the second computer data signal embodied in the carrier wave of the present invention, as the computer downloads the program in the computer data signal through a computer network or the like, and executes this program, it is possible to realize the above described first or second communication navigation system associated with the present invention. For example, the communication navigation terminal may be constructed such that it has a browser function and that the computer program to use is substantially or partially provided from the side of the communication center apparatus, as occasion demands.
Incidentally, the above object of the present invention can be achieved by another program storage device readable by a computer for tangibly embodying a program of instructions executable by the computer, which causes the computer to function as the communication center apparatus included in the above described first or second communication navigation system of the present invention (including its various aspects), more concretely, at various constitutional elements, such as the map database, the search device, the center side wireless device and the like, which constitute the communication center apparatus.
The above object of the present invention can be achieved by another computer data signal embodied in a carrier wave and representing a series of instructions which causes a computer to function as the communication center apparatus included in the above described first or second communication navigation system of the present invention (including its various aspects), more concretely, at various constitutional elements, such as the map database, the search device, the center side wireless device and the like, which constitute the communication center apparatus.
The above object of the present invention can be achieved by a first communication navigation method executed in a communication navigation system provided with: a communication center apparatus; and a communication navigation terminal, both of which transmit and receive information by a two-way communication through a communication network, the method provided with: (i) at the communication center apparatus, a search process of searching, by a predetermined algorithm, for a route heading to a destination from a current position of a movable body, according to the destination and the current position received through the communication network, on the basis of a map database for storing therein map database information including information for a route search, which enables the route search from the current position to the destination by the predetermined algorithm; and a center side wireless process of wirelessly transmitting route information indicating the searched route through the communication network, and (ii) at the communication navigation terminal, a measurement process of measuring the current position; a terminal side wireless process of transmitting the measured current position and receiving the transmitted route information through the communication network; a traveling locus recording process of recording a traveling locus of the movable body such that it preferentially holds the traveling locus recorded when the movable body is moving out of a service area of the communication navigation system; and a process of performing navigation processing of a predetermined type based on the preferentially held traveling locus in case that the movable body is moving out of the service area.
According to the first communication navigation method of the present invention, as is the case with the above described first communication navigation system of the present invention, since the traveling locus out of the service area is preferentially held by the traveling locus recording device, even in case that the movable body drives out of the service area later, it becomes still possible to perform the navigation processing of the predetermined type, such as the search for the route and the direction to be traveled and the like, on the basis of this preferentially held traveling locus.
The above object of the present invention can be achieved by a second communication navigation method executed in a communication navigation system provided with; a communication center apparatus; and a communication navigation terminal, both of which transmit and receive information by a two-way communication through a communication network, the method provided with: (i) at the communication center apparatus, a search process of searching, by a predetermined algorithm, for a route heading to a destination from a current position of a movable body, according to the destination and the current position received through the communication network, on the basis of a map database for storing therein map database information including information for a route search, which enables the route search from the current position to the destination by the predetermined algorithm; and a center side wireless process of wirelessly transmitting route information indicating the searched route through the communication network, and (ii) at the communication navigation terminal, a measurement process of measuring the current position; a terminal side wireless process of transmitting the measured current position and receiving the transmitted route information through the communication network; a traveling locus recording process of recording a traveling locus of the movable body; and a process of searching for at least one of a route and a direction to be traveled by the movable body as navigation processing of a predetermined type based on the measured current position and the recorded traveling locus in case that the movable body is moving out of the service area.
According to the second communication navigation method of the present invention, as is the case with the above described second communication navigation system of the present invention, in case that the movable body travels one area out of the service area, if there is recorded the traveling locus, which was obtained when having traveled within the same area in the past, it becomes still possible to surely search for at least one of the route and the direction to be traveled on the basis of this traveling locus and the current position.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with reference to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.